Although HIV testing and highly effective antiretroviral therapy (ART) have improved survival with HIV, the relatively low level of ART adherence presents a significant public health challenge in terms of the potential to transmit HIV. Men who have sex with men (MSM) accounted for 65% of new infections in the U.S in 2011. What is more concerning is that 60% of HIV+ MSM are not adherent to ART. Preventing transmission in virally unsuppressed HIV+ MSM who have unprotected anal intercourse (UAI) with serodiscordant partners can have a great public health impact. The proposed study has the potential to be cost-effective and scalable, which are goals of the National HIV/AIDS Strategy and the 2013 Trans-NIH Plan for reducing new HIV infections. As new HIV infections in MSM have been attributed in part to increased access to sex partners online, it is critical to deliver behavioral interventions to HIV+ MSM online to reach many high-risk men at a relatively low cost, engage HIV+ MSM where they meet sex partners, and enable men to participate privately on a computer, tablet, or Smartphone on their own schedule, as opposed to in a structured clinical setting. The first of our 3 theoretically-grounded HIV prevention videos about UAI, HIV disclosure, and testing in MSM was rigorously evaluated among MSM recruited online. In our single-session online video pilot for 971 MSM, we found significant reductions in UAI in the most recent encounter and significant increases in HIV status disclosure at 3-month follow-up, compared to baseline. In our subsequent online, single-session randomized controlled trial (RCT) for 3,092 MSM, we found significant reductions in UAI among MSM in the video arm at 60-day follow-up, compared to baseline; HIV+ MSM in the video arm reduced UAI, including serodiscordant UAI (SDUAI) at 60-day follow-up, compared to baseline. Based on our RCT findings on HIV+ MSM, we then tested our ability to recruit ethnically diverse HIV+ MSM. Our collaboration with POZ.com (POZ), the largest website for HIV+ individuals, was very successful. Through our prior work, we have identified a potentially highly effective and feasible risk reduction intervention approach for HIV+ MSM. We have also demonstrated success in engaging the target population. With the commitment of POZ and a strong team of experts, we propose to refine our intervention by editing our 3 HIV prevention videos into short doses for 10 online sessions (including boosters); targeting HIV+ MSM who are virally unsuppressed; monitoring self-reported clinical indicators (i.e., viral load); targeting online recruitment by rae and ethnicity to enroll equal numbers of HIV+ White, Black and Hispanic MSM for balanced representation; improving retention with incentives and a proven online platform; including educational information about ART adherence; and cost and cost-effectiveness analyses for potentially averted HIV infections to determine health-related cost savings. Online, we will recruit and follow a national sample of 1,500 high-risk, virally unsuppressed HIV+ MSM for 12 months.